A conventional rotary printing press has fountains for applying printing fluids to the press rollers, printing plates, and ultimately to the sheet or web being printed. Separate fountains are usually provided for ink and for water for each printing couple. Usually adjusters such as servomotors are provided across each fountain for controlling the ink or water supply provided by that fountain in incremental zones or columns across the fountain. By way of definition for purposes of this disclosure, in order to avoid confusion between the increment of the fountain controlled by a single adjuster and the larger increment controlled by a contiguous group of adjusters, the former will be referred to as a single or individual zone, and the term "zone", when used on its own is intended to refer to a plurality of contiguous single zones (i.e., a composite zone).
Control panels are associated with printing presses and have, among other control elements, an array of keys, such as mechanical switches or pushbuttons, for controlling the fountain adjusters. The keys are usually arranged in pairs (increase and decrease for each adjuster) in an elongated row, with the spacing between the keys often the same as the adjuster spacing across the fountain. By depressing a particular increase or decrease ink or water adjusting key, the position of the associated adjuster in the fountain is altered to supply more or less ink or water to the portion of the printed sheet controlled by the adjuster in question. Usually, such control panels also have a pair of ALL keys (one for each direction) which will adjust all of the adjusters in a selected fountain in the direction associated with the actuated ALL key.
European patent specification 0 047 926 discloses a system for inhibiting fountain adjusters in rotary presses wherein a microcomputer is programmed to respond to operation of a format selector key followed by operation of a "less ink" key in a selected inking unit to cause the ink adjusters, usually servomotors, to move into the neutral position with respect to the ink ductor and to stop. In the neutral position, the single zone associated with that adjuster supplies no ink to its area of the press. Until the "stop" instruction is cancelled, i.e., until the format selector key is actuated again, the adjusters in the deactivated single zones are inaccessible either for individual or joint ink zone adjustments, i.e., they are completely inactive until the stop instruction is cancelled.
The use of additional keys, such as the format keys described in connection with the aforementioned European patent specification, further complicates the control panel. Not only does the use of further specialized keys increase the complexity of the task presented to the pressman and make his job more difficult, but such specialized keys take up additional space on the control panel and require additional production and assembly costs. In addition, this known system of format selection is of limited flexibility since all that it is capable of doing is to inhibit (i.e., render inoperative) the fountain adjusters which ar deactivated.